Prior art systems having inward-facing cameras coupled to an eyeglasses frame, such as U.S. Pat. No. 9,672,416 titled “Facial expression tracking” to Zhang, try to detect facial expressions with just one camera that does not capture the eyebrows, and thus provides low accuracy. Other references, such as U.S. Pat. No. 8,573,866 titled “Head-mounted face image capturing devices and systems” to Bond, U.S. Pat. No. 8,289,443 titled “Mounting and bracket for an actor-mounted motion capture camera system” to MacKenzie, and U.S. Pat. No. 8,334,872 titled “Inverse kinematics for motion-capture characters” to Epps, are too bulky and thus are inconvenient for daily use. Therefore, there is a need for a new arrangement of inward-facing cameras on an eyeglasses-like frame, which is both comfortable for daily use and captures the required data for adequate facial expression detection.